The present invention relates to a current passing device of an EGR (exhaust gas recirculation) valve apparatus for constituting a recirculation system of, for example, an exhaust gas.
This kind of EGR valve apparatus in the prior art used a stepping motor as a valve opening/closing unit, but it has become to use a DC motor in place of the stepping motor in order to comply with increasing resolution, response and output power at the time of adjusting the opening of a valve.
FIG. 1 is a cross sectional view to show the current passing device of an EGR valve apparatus in the prior art. FIG. 2 is an enlarged cross sectional view of a relevant part of the device in FIG. 1. FIG. 3(a) is a perspective view to partially show a brush holding pipe portion in FIG. 2. FIG. 3(b) is an end view of FIG. 3(a).
In FIG. 1, a reference numeral 1 denotes a DC motor that is a driving unit (torque generating unit) of a valve for opening and closing an exhaust gas passage; a reference numeral 2 denotes a motor case thereof; a reference numeral 3 denotes a rotor rotatably supported in the motor case 2 via bearings 4, 5 and the rotor 3 has a screw hole 3a which is made to penetrate through at its axial center portion; a reference numeral 6 denotes a magnet mounted on the outer periphery of the rotor 3; and a reference numeral 7 denotes a stator core which is surrounding the outer periphery of the magnet 6 and a predetermined gap is formed between the stator core 7 and the magnet 6.
A reference numeral 8 denotes a coil that is arranged on both sides in the axial direction of the stator core 7 and constitutes a stator; a reference numeral 9 denotes a motor shaft that is a valve driving shaft and the motor shaft 9 is formed of a screw shaft and is screwed into the screw hole 3a of the above described rotor 3, thereby being moved in the axial direction by the rotation of the rotor 3.
A reference numeral 10 denotes a valve shaft abutting member that is integrally formed with the motor shaft 9 and a protruding end (right end in FIG. 1) of the valve shaft abutting member 10 abuts an end portion of a valve shaft (not shown) having the above mentioned valve at the tip thereof to make the valve shaft follow the movement in the axial direction of the above mentioned motor shaft 9 to thereby open and close the above described valve.
A reference numeral 11 denotes a cover member which is mounted on an end surface of the motor case 2 in a side of the valve shaft abutting member 10; a reference numeral 12 denotes a spring retaining member mounted on the protruding end side of the valve shaft abutting member 10; a reference numeral 13 denotes a valve urging spring which is mounted between the spring retaining member 12 and the above mentioned cover member 11 and the spring 13 urges the valve at the tip of the valve shaft via the valve shaft abutting member 10 in the direction to which the valve opens.
A reference numeral 14 denotes a commutator that rotates integrally with the rotor 3 and has an axial hole 14a at the center thereof.
A reference numeral 15 denotes a power source side case which is mounted on an opening end portion on a side of the commutator 14 of the motor case 2, and the power source side case 15 is made of one piece molded synthetic resin to constitute a main body of the current passing device of the DC motor 1 and is integral with a sensor built in portion 16 in which a position sensor (not shown) for detecting a degree of opening of the above mentioned valve is built and an input/output connector portion 17 in which a connector terminal is built.
In FIG. 1 and FIG. 2, a reference numeral 18 denotes a brush holding pipe portion integrally molded with a wall portion opposite to the commutator 14 of the power source side case 15; reference numerals 19 denote a plurality of axial slits which are made at the brush holding pipe portion 18; reference numerals 20 denote a plurality of brushes for passing current that are slidably inserted into the above mentioned brush holding pipe portion 18 and the brushes 20 are made of carbon particles and copper particles; reference numerals 21 denote a plurality of lead wires for passing current that are connected to the above mentioned brushes 20 and the lead wires 21 are extended from the slit 19 of the above mentioned brush holding pipe portion 18 and are connected to the connector terminal of the above mentioned input/output connector portion 17; reference numerals 22 denote a plurality of brush pressing springs which are received in the above mentioned brush holding pipe portion 18 and an urging force of the spring 22 puts the tip of the brush 20 into sliding contact with the above mentioned commutator 14. Herein, reference symbols 20a in FIG. 2 denote the worn particles of the brush 20.
Hereinafter, mounting the above mentioned brush 20 and mounting the power source side case 15 on the motor case 2 will be described.
First, when the brush 20 is mounted, in the first place the spring 22 is inserted into and received in the brush holding pipe portion 18 and then the brush 20 is inserted into the brush holding pipe portion 18 and when the brush 20 is inserted the lead wire 21 is slidably fitted in the slit 19, thereby mounting the brush 20 is finished. After the brush 20 is mounted, the power source side case 15 is fitted in and fixed to the opening end portion of the motor case 2 while the tip of the brush 20 is pressed onto the commutator 14, thereby mounting the power source side case 15 is finished.
Next, the operation of the device will be described.
When a direct current is supplied to the brush 20, the direct current is passed through the coil 8 after rectification by the commutator 14, so that an interaction between a magnetic field generated by the coil 8 and the magnetic field of the magnet 6 generates a rotational torque to the rotor 3. When the rotor 3 is rotated by the rotational torque, the motor shaft 9 screwed in the screw hole 3a of the rotor 3 is forced by the screws thereby to be moved linearly in the axial direction.
Herein, in the case where the motor shaft 9 is moved in the right direction in FIG. 1, the valve shaft abutting member 10 is pushed in a direction against the urging force of the spring 13 by the motor shaft 9 to open the valve via the valve shaft connected to the valve shaft abutting member 10. On the other hand, in the case where the motor shaft 9 is moved in the left direction in FIG. 1, the valve shaft abutting member 10 is made to follow the motor shaft 9 by the urging force of the spring 13 to close the valve via the valve shaft connected to the valve shaft abutting member 10.
Since the current passing device of the EGR valve apparatus in the prior art is constituted in the manner described above, it presents the following problems: the self-heating of the brush 20, which is caused when current is passed through the brush 20, and frictional heat, which is generated when the brush 20 is pressed onto the commutator 14, increase the ambient temperature of the brush holding pipe portion 18 to thermally deform the brush holding pipe portion 18 in the direction sandwiching the brush 20 as shown by a broken line in FIG. 3(b), to impair the sliding ability of the brush 20 by the thermal deformation, which results in poor contact between the brush 20 and the commutator 14. Thus, it is thought that a clearance between the brush holding pipe portion 18 and the brush 20 is increased in anticipation of the thermal deformation of the brush holding pipe portion 18, but in this case, there is presented another problem that the brush 20 has a too much allowance and hence causes noises.
Further, there is presented the following problem: since the above mentioned brush holding pipe portion 18 has a simple constitution in which it has the slit 19 for simply guiding the lead wire 21, when the power source side case 15 is mounted on the motor case 2 while the brush 20 is being pressed in a state where the spring 22 and the brush 20 are sequentially inserted into and set in the brush holding pipe portion 18, the brush 20 is jumped out of the brush holding pipe portion 18 by the resilience of the spring 22 to thereby impair the working property for mounting.
Still further, there are presented the following problems: when the DC motor 1 is started to operate, the brush 20 being in contact with the commutator 14 which is integrally rotated with the rotor 3 produces worn particles (carbon particles+copper particles) 20a and because no countermeasures are made against the worn particles 20a, the above mentioned worn particles 20a are suspended in the air and attached to the commutator 14 to thereby reduce the insulating ability of the commutator 14, or the above mentioned worn particles 20a enter a portion where the motor shaft 9 is screwed into the rotor 3 to thereby impair the movability in the axial direction of the motor shaft 9 when the rotor 3 is rotated, or still further, the above mentioned worn particles 20a enter inside of the sensor to thereby interfere with the function of the sensor.
The present invention has been made to solve the problems described above. It is an object of the present invention to provide a current passing device of an EGR valve apparatus that can prevent the thermal deformation of the brush holding pipe portion and can stably ensure the sliding ability of the brush.
Further, it is another object of the present invention to provide a current passing device of an EGR valve apparatus that can prevent a brush from being jumping out of the brush holding pipe portion by the resilience of the spring when a power source side case is mounted on a motor case to thereby improve working property for mounting.
Still further, it is further object of the present invention to provide a current passing device of an EGR valve apparatus that can prevent a reduction in the insulating ability of a commutator, a deterioration in the movability of a motor shaft, and a detriment to the function of the sensor all of those are caused by the worn particles of a brush.
A current passing device of an EGR valve apparatus in accordance with the present invention includes: a DC motor that has a commutator rotating integrally with a rotor and drives a motor shaft in an axial direction in connection with the rotation of the rotor to thereby open and close a valve; a power source side case that is provided with a sensor for detecting a position of the valve and an input/output connector portion and is mounted and set in a motor case of the DC motor; a brush that is mounted in the power source side case and is put into sliding contact with the commutator; and urging means for urging the brush in a direction that presses the brush onto the commutator, and it is characterized in that particle trapping means for trapping the worn particles of the brush is provided in the power source side case.
According to this constitution, the particle trapping means provided in the power source side case traps the worn particles of the brush and hence can prevent the worn particles from attaching to the surface of the commutator or entering a portion where the motor shaft is screwed into the rotor and entering the inside of the sensor, which results in producing an effect of preventing the deterioration in insulating ability of the commutator, deterioration in movability in the axial direction of the motor shaft, and detriment to the function of the sensor all of those are caused by the worn particles of the brush.
In the current passing device of an EGR valve apparatus in accordance with the present invention, the particle trapping means includes a particle attracting space formed by a rib for trapping particles that is provided in the power source side case.
According to this constitution, it becomes possible to effectively attract the worn particles of the brush in the particle attracting space and thus to produce an effect of improving the performance of trapping the worn particles.
In the current passing device of an EGR valve apparatus in accordance with the present invention, a web like rib is formed on the inside wall surface of the power source side case to form a plurality of particle attracting spaces.
According to this constitution, it becomes possible to produce an effect of further improving the performance of trapping the worn particles of the brush by the plurality of particle attracting spaces. Further, the web like rib can produce an effect of increasing the strength of the power source side case.
In the current passing device of an EGR valve apparatus in accordance with the present invention, the surface of the rib and the bottom surface of the particle attracting space are made rough.
According to this constitution, since the surface of the rib and the bottom surface of the particle attracting space are made rough, they can produce an effect of further improving the performance of attracting and trapping the worn particles of the brush.
A current passing device of an EGR valve apparatus in accordance with the present invention includes: a DC motor that has a commutator rotating integrally with a rotor and drives a motor shaft in an axial direction in connection with the rotation of the rotor to thereby open and close a valve; a power source side case that is provided with a sensor for detecting a position of the valve and an input/output connector portion and is mounted and set in a motor case of the DC motor; a brush holding pipe portion that is mounted on the power source side case; a brush that is slidably inserted into the brush holding pipe portion and is put into sliding contact with the commutator; and urging means that is built in the brush holding pipe portion for urging the brush in a direction that presses the brush onto the commutator, characterized in that rib to prevent thermal deformation is provided on the brush holding pipe portion.
According to this constitution, it becomes possible to prevent the thermal deformation of the brush holding pipe portion and thus to produce an effect of ensuring the stable slidability of the brush.
In the current passing device of an EGR valve apparatus in accordance with the present invention, rib to prevent thermal deformation is formed continuously integrally with a rib for trapping particles that is provided in the power source side case to form a particle attracting space.
According to this constitution, it becomes possible to surely prevent the thermal deformation of the brush holding pipe portion and to form the thermal deformation preventing rib integrally with the particle trapping rib, which results in producing an effect of easily forming the ribs.
A current passing device of an EGR valve apparatus in accordance with the present invention includes a brush falling out preventing means to prevent the brush which is slidably inserted into a brush holding portion and is urged in the direction that puts the brush into sliding contact with a commutator, from falling out of the brush holding pipe portion.
According to this constitution, it becomes possible to prevent the brush from jumping out of the brush holding pipe portion when the power source side case is mounted on the motor case, which results in producing an effect of improving workability in mounting the power source side case.
In the current passing device of an EGR valve apparatus in accordance with the present invention, a pressing piece portion which presses a lead wire connected to the brush on a tip side of the brush holding pipe portion, is formed on a portion of the sensor component as the brush falling out preventing means, on a portion of a sensor component.
According to this constitution, it becomes possible to prevent the brush from jumping out of the brush holding pipe portion by pressing the lead wire of the brush that is inserted into the brush holding pipe portion and is urged in the direction that presses the brush into sliding contact with the commutator by means of the pressing piece portion on the side of the sensor. For this reason, it becomes possible to easily insert and set the brush into the brush holding pipe portion and to easily mount the power source side case on the motor case, which results in producing an effect of improving workability. Further, since the above mentioned pressing piece portion presses the lead wire on the tip side of the brush holding pipe portion, it becomes possible to produce an effect of ensuring a sliding stroke responsive to the wear of the brush.
In the current passing device of an EGR valve apparatus in accordance with the present invention, a lead wire engaging protrusion is formed on a tip of the brush holding pipe portion having a slit in which a lead wire connected to the brush is fitted, and that extends in a direction that blocks the slit as the brush falling out preventing means.
According to this constitution, only by forming the lead wire engaging protrusion on the tip of the brush holding pipe portion, it becomes possible to produce an effect of preventing the brush from jumping out of the brush holding pipe portion and of ensuring a sliding stroke responsive to the wear of the brush.
In the current passing device of an EGR valve apparatus in accordance with the present invention, when the brush is inserted into the brush holding pipe portion, the lead wire connected to the brush is fitted in the slit of the brush holding pipe portion and then a portion of the tip of the brush holding pipe portion is bent in the direction that blocks the above mentioned slit to form lead wire engaging protrusion.
According to this constitution, when the lead wire is fitted in the slit of the brush holding pipe portion, it becomes possible to produce an effect of easily fitting the lead wire in the slit without the interference of the lead wire engaging protrusion and of preventing the brush from jumping out of the brush holding pipe portion.
A current passing device of an EGR valve apparatus in accordance with the present invention includes a filter to prevent entry of worn particles of the brush which is disposed between the commutator and a front end face of the sensor portion mounted on the power source side case.
According to this constitution, it becomes possible to prevent the worn particles of the brush from entering a portion where a motor shaft is screwed into a rotor and the inside of a sensor, which results in producing an effect of normally ensuring the movability of the motor shaft and the function of the sensor.